Research subjects sometimes receive payment.
Patients are usually reimbursed for their travel expenses. You do not need to pay for medicinal products that you are given during the research. This does not apply to registered medicinal products. However, those are usually reimbursed by your health insurer.
Healthy volunteers often receive a payment. The amount depends on how long the research lasts and how much of a burden it places on participants. That is related to the number of measurements and any inconvenience. The payment is not dependent on the risk of the research and is based on the minimum wage. The medical research ethics committee (MREC) that assesses the research checks the amount of the payment. The payment is usually a gross amount. You may be obliged to report the payments to the Tax and Customs Administration.